A tweet with a photograph of a man in boxer briefs was sent in late May to a female college student from the Twitter account of Rep. Anthony Weiner, D-N.Y. The fiery congressman at first denied that he had sent the tweet, claiming his account had been hacked. But he refused to say whether he was the man pictured in the image.

As more women came forward with photos of the congressman, Weiner eventually admitted having relationships with six women via Internet and cell phone. He said he had sent the first revealed tweet by accident, believing it to be a private message.

"I take full responsibility for my actions," Weiner said. "The picture was of me, and I sent it."

Two days later, ABC News learned that Weiner's wife and aide to Secretary of State Hillary Clinton, Huma Abedin, was pregnant with the couple's first child. Abedin, 35, chose to stay with Weiner despite the scandal. Weiner resigned from his seat and the couple welcomed their child, Jordan Zane Weiner, Dec. 23.

The second-term congressman from New York was little known outside of Washington, that is, until his bare, muscular chest became an Internet sensation. In January, a shirtless self-portrait that Lee reportedly sent to a 34-year-old woman he met on Craigslist surfaced on the gossip website Gawker.

Lee, a married father of one, first tried to dispel rumors of an extramarital affair, but then abruptly resigned when it became clear that the scandal wasn't going away.

"I regret the harm that my actions have caused my family, my staff and my constituents. I deeply and sincerely apologize to them all. I have made profound mistakes and I promise to work as hard as I can to seek their forgiveness," Lee said in a statement.

Herman Cain's fall came just as quickly as his rise to the top. The Tea Party star, once considered a favorite to be the 2012 Republican presidential nominee, dropped out of the race after being dogged by multiple allegations of sexual harassment and a claim of an extramarital affair.

Two women publicly claimed they were the subjects of inappropriate physical behavior by Cain when he served as head of the National Restaurant Association in the late 1990s. A third woman did not want to be identified. Two official complaints were filed against Cain at the time.

A fourth woman, Atlanta businesswoman Ginger White, said she had a long affair with Cain. The former businessman denied that charge, although he said White was a friend who he was supporting financially.

The former chief executive of Godfather's Pizza denied the allegations against him but could not overcome the political fallout.

The little-known congressman from Oregon grabbed headlines earlier this year for his erratic behavior that sparked multiple calls for his resignation.

Leaked emails from the Yale Law School graduate's federally issued BlackBerry show him demonstrating bizarre behavior, including a photo of him in a tiger costume. Other emails were written in the voice of his adolescent children. Wu said the photos were taken while he was "joshing around" with his children and that he would undergo mental health treatment and take medication.

Several members of Wu's staff also told local newspapers that he was increasingly unpredictable on the campaign trial and in private last fall, and had several angry and loud outbursts.

The Oregonian also reported in the summer that Wu was accused of an unwanted sexual encounter with the 18-year-old daughter of a childhood friend.

The seven-term congressman resigned in August amid pressure from his fellow Democrats.

Arnold Schwarzenegger, the Hollywood actor-turned California governor, had long been the subject of news reports about alleged extramarital affairs. But the allegations turned to fact when Schwarzenegger revealed in May that he had a love-child with a former household staffer who worked in the family home as a housekeeper and assistant for more than 20 years, until this January.

Birth records showed that Schwarzenegger's youngest son with wife Maria Shriver and his love child were born less than a week apart. The mother of the love child, Mildred Patricia Baena, listed her then-husband as the boy's father on the child's birth certificate in 1997. She filed for separation three weeks later.

After the reports, Schwarzenegger's high-profile wife filed for divorce.

John Ensign resigned in April after an investigation into his affair with his best friend's wife and his alleged attempts to cover it up.

Political observers said the Republican senator from Nevada resigned to avoid facing an expulsion after a scathing report by the Senate ethics panel detailing his alleged attempts at covering up an extramarital affair with Cindy Hampton, the wife of his former top aide, Doug Hampton. The affair had occurred while Doug Hampton -- Ensign's best friend -- was employed by the senator, according to the report. It also stated that Ensign tried to cover up the sex scandal, made false statements to the Federal Election Commission and violated campaign finance laws.

The criminal investigation into Solyndra, a failed solar power company that received a half-billion dollar loan guarantee from the government, became a political lightning rod this year.

Despite early warning signs the company could be heading for trouble, Solyndra was awarded a $535 million loan guarantee in 2009 by the Obama administration. It went bankrupt despite the financial aid. Republicans charge that the troubled company received money because of its heavy political connections. One of Solyndra's major investors was George Kaiser, an Oklahoma billionaire who raised between $50,000 and $100,000 for Obama during the 2008 election.

Congress has opened an investigation into the loan granted by the Department of Energy. President Obama has maintained the Solyndra got the loan "on merits."

The Justice Department is under fire for failing to catch a program under which U.S. guns were allowed to flow illicitly into Mexico under the watchful eyes of federal agents.

In September 2009 , the Bureau of Alcohol, Tobacco and Firearms launched a controversial strategy allowing guns to flow into Mexico while the agency tried to identify and charge upper-level cartel members who were buying the guns. The guns, however, turned up in numerous crime scenes in Mexico, including murders. And at least one of the weapons was recovered at the scene where U.S. Border Patrol Agent Brian Terry was gunned down.

Obama and Attorney General Eric Holder have come under scrutiny by some Congressional Republicans who allege high-ranking administration officials were aware of the program, known as "Fast and Furious," and its flaws, but did not intervene.In October, Obama said he had "complete confidence" in Holder to oversee a Justice Department investigation into the gun-running operation.